what kind of work do you do on 10-wheelers?
I disagree with Rod, if my brakes go when I've got the duece up to top speed I'm not touching the parking brake. I honestly don't think it would assist me. I would downshift to 4th, drop the T-case to low, and depending on traffic/pedestrian conditions I would start looking for emergency routes to avoid loss of life. Better to run smack into a tree and risk killing yourself than risk killing other people. Also better to use a thick tree or a deep ditch as a crumple zone than to use the crumple zone of the Kia or Hyundai in front of you.
Are there more steps that I would take if my brakes went out? Sure, but what you do in the first five seconds of an emergency situation have a domino effect that ultimately determines whether everyone can sleep at home that night.
If I had to move a duece without brakes, I would be in low range, and never get out of the first 3 gears. I probably wouldn't shift out of 1st.
Signs--a lot of guys here get bent out of shape regarding a cavalier attitude towards maintenance and inspection. Please don't drive your truck on the road without any brakes to get to the garage you're intending to do your tear-down at. It sounds silly to even mention it, but some people are born stupid enough to think that brakes are optional for an on-road vehicle.